Two years after Saudi Arabia and its Gulf allies rejected OPEC's attempt to intervene in oil markets to counter collapsing prices, Riyadh is rallying support for collective action. On Sept. 28, OPEC members tentatively agreed to cut production to between 32.5 million and 33.0 million barrels per day. However, output has continued to rise, meaning even deeper cuts will be required than before to reach this mark. The moment of truth will come Nov. 30 at OPEC's semiannual summit in Vienna, where member states will seek to finalize a deal on production cuts. Though Saudi Arabia has worked hard to convince other member states to support an agreement, the bloc remains divided over how much output to cut as a whole -- and how much of the burden should be carried by each member. They are questions under debate this week, so as to finalize an agreement before the main...